1. Field of the Invention
The present invention relates to a vehicle-installed remote control unit for remotely controlling various parts of a vehicle in response to command signals transmitted from a vehicle dedicated portable transmitter.
2. Description of Related Art
There is known a key-less entry system for remotely locking and unlocking doors of a vehicle in response to command signals radio-transmitted from a portable transmitter carried by a user of the vehicle (refer to Japanese Patent Applications Laid-open No. 2002-129794 and No. 9-41754, for example).
In the key-less entry system, there is a possibility that the remote door lock or unlock operation is not performed despite the manipulation of the portable transmitter when the vehicle is parked near an electromagnetic radiation source such as a power transmission plant or a broadcast antenna, because the vehicle-installed remote control unit cannot detect a command signal transmitted from the portable transmitter when a large noise is emitted from the electromagnetic radiation source.
When such a system inoperative has occurred, to diagnose its cause, it is necessary to determine whether it relates to the ambient noise or device malfunction in the first place.
It is common that, when a car dealer or a car maker has received a complaint from a car user about the inoperative of a remote control system such as the key-less entry system, they send engineers to the scene together with a measuring instrument such as a spectrum analyzer to make a survey on the radio wave conditions around the vehicle or the vehicle-installed remote control unit.
Accordingly, finding the cause of the inoperative of the remote control system has been a troublesome and time-consuming task.